1. Field of the Invention
The present invention relates to a pneumatic tire which can improve a wear performance and an on-road performance while retaining an off-road performance and a drainage performance.
2. Description of the Related Art
Generally, in a tire which is used in an off-road traveling, there is employed a block pattern provided with a lot of blocks on a tread surface, so that a traction (a traction force) can be achieved on a gravel road or a muddy place. However, on the contrary, in an on-road traveling, since the blocks tend to tilt and deform at a time of driving and braking or a time of cornering particularly in a case where a vehicle weight is large, the wear performance and the on-road performance (the on-road traveling performance) are hard to be sufficiently achieved. Further, in this kind of tire, it is important to suppress the occurrence of hydroplaning while retaining the drainage performance.
In Japanese Unexamined Patent Publication No. 2002-29224, there is described a pneumatic tire in which at least two block rows are comparted by a lateral groove, and a reinforcing portion connecting a side surface of the block on one side thereof and a bottom portion of the lateral groove is overlapped on the block on the other side in a tire width direction, for the purpose of achieving an off-road performance, a snow performance and an on-road performance. However, in this tire, although it is possible to support the block which tends to tilt in a tire circumferential direction by the reinforcing portion, it is insufficient for suppressing a tilting deformation in the tire width direction, so that it is not provided with a structure for improving the drainage performance, as well as it is impossible to improve a wear performance and the on-road performance at a cornering.
In Japanese Unexamined Patent Publication No. 2008-222088, there is described a pneumatic tire in which land portion row is constituted by alternately providing a first land portion and a second land portion which are comparted by a lateral groove in a tire circumferential direction, and a V-shaped groove is formed in the land portion row by overlapping an inclined surface portion of the first land portion and an inclined surface portion of the second land portion in a tire width direction. However, even in this tire, it is insufficient for suppressing a tilting deformation of a block in the tire width direction, and does not assume an off-road traveling, as a matter of course.